308 Progress in Science. [July, 
Channel traffic, and having a suspended saloon made unsusceptible to 
transverse oscillation by the application to it of special hydraulic machinery: 
This vessel is 350 ft. in length, and 4o ft. actual beam; she also possesses 
the peculiarity of having two distinct sets of engines, and two pairs of paddles, 
placed 105 ft. apart between centres; whilst, with the view of reducing the 
pitching motion as much as possible, she has been constructed with low 
ends. How far the vessel may prove a success is at present uncertain, and 
probably some further experience may be necessary before the swinging 
saloon is brought to such a state of perfection as fully to accomplish the 
desired end of insuring travellers against the terrors of sea-sickness. 
Docks, &c.—A new public graving-dock has recently been opened at Cardiff 
in connection with the Roath Basin. The side walls of the dock are of 
Forest and Radyr stone, and the bottom of the whole is limestone, surrounded 
by a stone coping. Slips are provided each side, and the entrance, 60 ft. in 
width, is fitted with an immense caisson. The dock is 600 ft. in length, and 
78 ft. wide; the depth of water provided will be, during spring tides, 23 ft.; 
and during neap tides 13 ft., but the depth of water will rarely fall below 17 ft. 
The water can be discharged in about four hours, through the instrumentality 
of two powerful steam pumps. 
Railways.—A very great advance towards removing that element of human 
fallibility which has so often been the cause of serious railway accidents, has 
recently been made by the introduction of an electric block signal, the 
combined invention of Messrs. Farmer and Tyer. This apparatus comprises 
a combined mechanical and electrical arrangement by means of which the 
working of the semaphore signal can he controlled from any point, quite 
irrespective of distance. Electricity is employed to a& on an eleftro-magnet, 
causing it to attraét an armature; when the attraction ceases, a detent in 
connection with the armature is released, and the signal is set free from the 
hand-lever by a mechanical arrangement, and by means of the usual counter- 
weight the semaphore on the line rises to and remains at danger dire@ly 
the connection between it and the hand-lever is broken. By the use of this 
invention the signalman at either end of any block section has the power 
individually to act upon the semaphore to signal danger, but it is only by 
the concurrent action of the two that the safety signal can be given. 
A very simple contrivance has recently been introduced upon the Great 
Western Railway of Canada, which promises to be of service by giving the 
engine-driver always a view over the whole train, and which promises to be of 
valuable assistance in the operating of goods trains, and would also be a 
useful adjun& for passenger train service. The device consists of the intro- 
duction of a mirror placed on the engine weather plate, immediately in front, 
and over the heads of the driver and fireman, at such an angle as to reflect a 
view of the whole cf the wagons or carriages attached to the engine, and thus 
render the train behind as distinétly visible to the driver and fireman as the 
line itself in front. 
At the time we are writing some important experiments are being made on 
the Midland Railway with different systems of continuous brakes, an account 
of which we hope to be able to give in the next number of the ‘ Quarterly 
Journal of Science.” 
In San Francisco a system of wire rope street tramways has recently been 
introduced, which presents some features of novelty. In consists of an 
endless wire rope placed in a tube below the surface of the ground, between 
the tracks of the line, and kept in position by means of sheaves, upon and 
beneath which the rope is kept in constant motion during the hours the traffic 
is running, by a stationary engine, the power being transmitted from the 
motor to the rope by means of grip pulleys, and from the rope to the cars 
on the street by means of a gripping attachment fastened to the car, and 
which passes through a narrow slot in the upper side of the tube. 
